Boundary Analysis for H 2 Production by Fermentation

Transcription

1 National Renewable Energy Laboratory Innovation for Our Energy Future A national laboratory of the U.S. Department of Energy Office of Energy Efficiency & Renewable Energy Boundary Analysis for H 2 Production by Fermentation July 2001 September 2004 Subcontract Report NREL/SR May 2005 T. Eggeman Neoterics International Lakewood, Colorado NREL is operated by Midwest Research Institute Battelle Contract No. DE-AC36-99-GO10337

2 Boundary Analysis for H 2 Production by Fermentation July 2001 September 2004 Subcontract Report NREL/SR May 2005 T. Eggeman Neoterics International Lakewood, Colorado NREL Technical Monitor: M.K. Mann Prepared under Subcontract No. LCO National Renewable Energy Laboratory 1617 Cole Boulevard, Golden, Colorado Operated for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy by Midwest Research Institute Battelle Contract No. DE-AC36-99-GO10337

3 This publication was reproduced from the best available copy Submitted by the subcontractor and received no editorial review at NREL NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Available electronically at Available for a processing fee to U.S. Department of Energy and its contractors, in paper, from: U.S. Department of Energy Office of Scientific and Technical Information P.O. Box 62 Oak Ridge, TN phone: fax: mailto:reports@adonis.osti.gov Available for sale to the public, in paper, from: U.S. Department of Commerce National Technical Information Service 5285 Port Royal Road Springfield, VA phone: fax: orders@ntis.fedworld.gov online ordering: Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste

4 Introduction The Hydrogen Program of the U.S. Department of Energy is examining novel methods for hydrogen production. One potential means for hydrogen production is the fermentation of glucose or other carbohydrates: C 6 H 12 O H 2 O => 12 H CO 2, (Glucose) G o = -16 kj/mol Theoretically, up to 12 moles of hydrogen can be produced per mole of glucose consumed. This report presents a boundary analysis for this approach. A simplified overall material and energy balance along with order-of-magnitude economics are presented. Design Summary The design basis assumed a hydrogen production rate of 50 MMSCFD at 435 psig. Figure 1 is a block flow diagram. The simplified material balance and utilities summary were computed with the assistance of Aspen Plus 10.2 (files: E0312b). The base case assumes a yield of 10 moles of hydrogen per mole of glucose, with a glucose concentration of 3 wt% in feed to fermentation. The remaining fraction of the glucose is assumed to either be unconverted or diverted into cell mass production. No cost or value was associated with disposal of the cell mass stream. Also, no costs for nitrogen and other nutrient sources are included in the analysis. A battery limits addition to an existing biorefinery is envisioned. The host facility will provide glucose, water, utilities and other infrastructure as a variable operating cost for the new facility. The fixed capital investment is limited to the battery limits unit; in other words, no capital for upgrades to the host facility s infrastructure is included in the base case. Conceptually any carbohydrate source could be used as a feedstock for the fermentation. Corn starch hydrolyzate, juices from sugar cane or sugar beet processing, wood fiber hydrolyzates from pulp mills, or biomass hydrolyzates from agricultural resides, energy crops and other biomass sources are among the many possible sources. Many of these potential feedstocks would actually produce a mixture of sugars upon hydrolysis. To simplify the analysis, I assumed that carbohydrate was present only in the form of glucose. The presence of a mixed carbohydrate feedstock and its impact on the design were not considered in this preliminary analysis. A few statements are needed to put the scale of this plant into perspective. By today s standards, a 50 MMSCFD hydrogen plant would be a large, but not world-scale, industrial hydrogen production facility. The amount of carbohydrate required to feed this facility roughly corresponds to the total carbohydrate present in 2,000 metric tons per day of corn stover. This feed rate corresponds to the rate used in the 2002 NREL Design Case for bioethanol production (1). The NREL design case assumes corn stover is collected from a 50 mile radius around the 1

5 plant and is projected to produce 69.3 MMgal of ethanol per year. In terms of starch hydrolyzate from corn, the projected feed rate corresponds to a grind rate of roughly 80,000 bushels per day. This would be considered a medium scale corn dry milling facility or a small scale corn wet milling facility. Results Table 1 summarizes the projected fixed capital investment. Individual cost items were obtained as follows: 1) Fermentation Unit Taken to be the same as for the fermentation unit in the 2002 NREL Design (1) (i.e. costing by analogy with a similar process) 2) Raw Gas Compressor - Estimated using Questimate, a commercially available software program for generating equipment costs. 3) PSA Estimated on H 2 production rate and internal cost curves. 4) Cell Recovery Unit A detailed definition of the unit is not available; a reasonable capital allocation was assumed. 5) Other The balance of plant was assumed to be 50% of the identified equipment. The total fixed capital is projected at $73.6MM, or a fixed capital investment of $1.47MM per MMSCFD of H 2 production. For comparison, the standard industry rule-ofthumb for fixed capital costs for production of hydrogen by steam methane reforming are $1.00MM per MMSCFD of H 2 in this capacity range, although recent facilities have had slightly lower requirements (2). Table 2 summarizes projected plant level operating costs. Glucose is the major operating cost driver. The base case assumed that glucose was available at $0.05 per lb (dry). This is approximately the value placed on dilute, unfinished sugar streams in today s corn processing facilities. The US DOE goal for the cost of sugar in biomass hydrolyzates is $0.07 per lb in Year Long term goals for US DOE are to reduce cost of biomass derived sugars into the $0.03- $0.05 per lb range. Steam, electricity, and depreciation are other important operating cost drivers. Steam costs are driven by the assumed need to heat sterilize the fermentation media. Steam usage is sensitive to the glucose concentration in the media. Electricity costs are driven by the power needs of the raw gas compressor. The simulation assumed the inlet suction pressure of the raw gas compressor was 14.7 psia. Pressurized operation of the fermentation vessels may reduce the compression work requirements and compression capital, at the expense of increased capital for fermentation. 2

6 Table 3 summarizes projected revenues. Nearly 95% of the revenues are derived from hydrogen. The byproduct fuel gas, derived from the PSA tail gas, was valued on a heating value basis using industrial natural gas as the proxy. The discounted cash flow calculations use the rational pricing rather market pricing method. For rational pricing, the hydrogen sales price required for a 10% after tax real internal rate of return for the project under the assumptions of 100% equity financing and 40 years of operation is calculated. The calculated required price does not reflect the market value of the hydrogen product. Figure 2 displays the projected cumulative cash flows. Breakeven occurs between Year 8 and Year 9 of operation. Faster times to breakeven can be had by either increasing the required discount rate (i.e. making the required hydrogen selling price higher) or by increasing the amount of debt financing. Figure 3 displays contributions to the calculated required price for hydrogen. Glucose feedstock, utilities, and capital are the major drivers. Sensitivity Analysis Figure 4 shows the effect of hydrogen yield and the cost of glucose on the feedstock cost component. The base case assumed 10 moles H 2 per mole glucose and $0.05 per lb (dry) for glucose. The effect on the required hydrogen prices of changing these assumptions can be estimated using Figure 4 to adjust for the feedstock portion of the required hydrogen price. Note that other cost components such as capital and non-feedstock operating costs are not included in this figure. One opportunity for reduced hydrogen price is finding waste feedstocks or taking advantage of R&D advancements in the biomass feedstock preparation area. If the feedstock could be obtained for $0.03/lb of glucose, the required hydrogen price would be reduced to $1.60/kg. At a zero feedstock price (representing a niche-market waste), the required hydrogen price is reduced to $0.90/lb. Figure 5 shows the sensitivity of the required hydrogen price with respect to variations in fixed capital. Since the economics are dominated by the cost of carbohydrate, the effect of variations in fixed capital are somewhat muted. Glucose concentration in the fermentation feedstock will affect both the amount of steam required for heat sterilization and the capital cost for the fermentation unit. Calculating the exact projections for the effect of glucose concentration on the required hydrogen price is involved. A rough estimate can be generated by just looking at the impact on steam usage. Lowering the glucose concentration in the feed from 3 wt% to 1.5 wt% doubles the amount of water present in the feed, which in turn doubles the heat load for sterilization, or adds another ~$0.23 per kg H 2 to the required hydrogen price. Figure 6 shows the sensitivity of the required hydrogen price with respect to variations in the required internal rate of return. The figure shows that the required internal rate of return has a significant impact on the projected economics. 3

7 Conclusions The cost of carbohydrate and the yield of hydrogen from carbohydrate appear to drive the economics in the best case scenario considered in this report. It is questionable whether deployment of resources needed to develop this method of hydrogen production is justified, given the fact that the long term goals of the Hydrogen Program require costs lower than those projected by this analysis. The use of lower-priced feedstocks could reduce the required selling price of hydrogen to as low as $ /kg hydrogen. An assessment of the availability of these feedstocks and the real potential for R&D to produce low-cost sugars is needed. References (1) Aden, A., Ruth, M., Ibsen, K., Jechura, J., Neeves, K., Sheehan, J., Wallace, B, Montague, L., Slayton, A., Lukas, J., Lignocellulosic Biomass to Ethanol Process Design and Economics Utilizing Co-Current Dilute Acid Prehydrolysis and Enzymatic Hydrolysis for Corn Stover, NREL/TP , June (2) Fleshman, J.D. in Chapter 6.2 of Meyers, R.A. (ed.), Handbook of Petroleum Refining Processes, 2 nd ed., McGraw-Hill,

8 Table 1 - Fixed Capital Summary Direct $MM (2000) Fermentation Unit 10.0 Raw Gas Compressor 11.3 PSA 10.9 Cell Mass Recovery Unit 4.0 Other 18.1 Total 54.4 Indirects Engineering & Design 4.4 Construction Expense 5.4 Contractor's Fee 2.7 Total 12.5 Contingency Depreciable Fixed Capital w/o Contingency 66.9 Contingency 6.7 Depreciable Fixed Capital 73.6 Non-Depreciable Fixed Capital 0.0 Total Fixed Capital 73.6 Fixed Capital, $MM/MMSCFD of H

9 Table 2 - Operating Cost Summary (Plant Level) Variable $/yr $/kg H2 Raw Materials Glucose 40,789, Subtotal 40,789, Utilities Steam 7,993, Electricity 7,507, Other 799, Subtotal 16,301, Other 735, Subtotal 735, Total Variable 57,826, Fixed Labor 1,248, Maintenace Labor 919, Maintenance Materials 1,839, Property Taxes & Insurance 1,471, General and Adminstrative 249, Depreciation (10 yr SL) 7,358, Total Fixed 13,087, Cash Costs 63,555, Operating Costs 70,913, Table 3 - Revenue Summary Item $MM (2000)/yr $/kg H2 Hydrogen Fuel Gas Total

10 Figure 1 Design Summary Raw Gas Compression PSA H2 Product Fuel Feed Feed Prep Fermentation KO Liquid Stream Summary American Standard Units Cell Recovery Cell Mass Water Stream Feed H2 Fuel KO Cell Water Product Gas Liquid Mass Temperature, F Pressure, psia Components, lb/hr H2 0 11,067 1, CO , Water 3,763, ,547 77,760 3,613,880 Glucose 116, ,440 0 Total, lb/hr 3,880,258 11, ,525 13,547 97,247 3,613,880 SI Units Stream Feed H2 Fuel KO Cell Water Product Gas Liquid Mass Temperature, C Pressure, kpa Components, kg/hr H2 0 5, CO , Water 1,707, ,145 35,272 1,639,230 Glucose 52, ,818 0 Total, kg/hr 1,760,057 5,020 65,555 6,145 44,111 1,639,230 Utilities Summary Steam Electricity Duty, Steam, Power, Power, Exchanger MMBtu/hr lb/hr Item hp (Shaft) kw (Motor) H ,899.6 C , ,446.4 Total 185,899.6 P Other 1,000.0 Total 21,

11 Figure 2 - Cumulative Cash Flow 500. Cumulative After Tax Income, $MM Breakeven Year of operation Figure 3 - Category Cost Contributions $1.4 Contribution to Required Hydrogen Selling Price ($/kg) $1.2 $1.0 $0.8 $0.6 $0.4 $0.2 $0.0 -$0.2 $0.36 $1.17 $0.00 Capital Cost Feedstock Cost Other Raw Material Fixed O&M Cost Other Variable O&M Cost $0.16 $0.50 Byproduct Credit -$0.11 8

12 6 5 Figure 4 - Sensitivity of Feedstock Cost Component vs. Fermenation Yield and Glucose Cost (Cost includes affect of H 2 loss in PSA; No capital or non-feedstock operating costs are included) per lb (dry) per lb (dry) per lb (dry) per lb (dry) Design Raw Material Cost, $/kg H Fermentation Yield, mol H 2 /mol Glucose Figure 5 - Sensitivity wrt Fixed Capital $2.35 $2.30 Design $2.25 Required H2 Price, $/kg $2.20 $2.15 $2.10 $2.05 $2.00 $1.95 $ Fixed Capital, $MM (2000) 9

13 Figure 6 - Effect of IRR on Required H 2 Price Required H 2 Price, $/kg Design Internal Rate of Return, After Tax - Real 10

14 Bioprocess Energy Chemicals Polymers NEOTERICS INTERNATIONAL Using Technology to Create Business Innovation S. Ellis Ct. Lakewood, CO March 12, 2004 Margaret Mann National Renewable Energy Laboratory 1617 Cole Boulevard, MS 1613 Golden, CO Dear Maggie: Enclosed is a conceptual design and order-of-magnitude economic analysis for the production of hydrogen by fermentation of carbohydrates under the following design basis: Production Rate: Plant Type: Utilities: 120,480 kg H 2 /day Battery limits with no capital required for OSBL expansions Purchased from host facility Fermentation Yield, moles H 2 per mole Glucose 10 Cost of glucose, $/lb (dry) 0.05 Nitrogen and other nutrient sources None Waste treatment costs None The results of the economic analysis are: Fixed Capital, $MM (2000) 73.6 Required H 2 Price, $/kg H where the required H 2 price is defined as the price required for a 10% after-tax real internal rate of return under the assumption of 100% equity financing and 40 years of plant operation. The results projected by this study should be considered as a best case scenario. The assumed technical performance could only be achieved after significant long-term research. Sensitivity analysis shows major economics drivers include: fermentation yield, cost of glucose, fixed capital, glucose concentration in the fermentation and various financial assumptions. Sincerely, Tim Eggeman, Ph.D., P.E. 11

15 Bioprocess Energy Chemicals Polymers Addendum NEOTERICS INTERNATIONAL Using Technology to Create Business Innovation S. Ellis Ct. Lakewood, CO July 29, 2004 Margaret Mann National Renewable Energy Laboratory 1617 Cole Boulevard, MS 1613 Golden, CO Dear Maggie: This letter is a follow up on several issues raised at the US DOE Workshop on Hydrogen Production via Direct Fermentation held on June 9, 2004, in Baltimore, MD. 1) Operating Capacity Factor: The original analysis assumed an 80% operating capacity factor. I re-ran the economics using a 95% operating capacity factor. The required H 2 selling price drops from $2.077 per kg to $1.955 per kg. This change only makes a small change in the economics, thus the main conclusions of the report are unaffected. 2) Fermentation Assumptions: The report is an order-of-magnitude estimate for the economics of hydrogen production assuming significant improvements in the technology. I assumed that the fermentation was anaerobic, the feed sugar concentration was 30 g/l and the capital cost would be similar to that projected for the fermentation section of bioethanol plants processing a similar amount of feedstock. The current NREL design model for bioethanol production uses a simultaneous saccharification and fermentation design. The rate controlling step is hydrolysis of the complex carbohydrates into simple fermentable sugars, so volumetric productivity is independent of fermentation kinetics. It is too early to speculate on the relative rates of hydrogen production by fermentation vs. saccharification kinetics, but in essence I ve assumed the fermentation kinetics will be faster than saccharification. 3) Sanitation Requirements: I envision the sanitation needs for this plant to be similar to those of today s ethanol production facilities. The feeds would be heat sterilized, but the plant would not require extreme levels of sterility. The assumed sugar feed concentration is fairly low for an industrial fermentation. Higher sugar concentrations would reduce steam usage for sterilization, but may lead to issues with feed inhibition. 4) Cell Mass Value: I assigned a zero value to the cell mass. The value of the cell mass depends upon whether it can be sold or has to be treated as a waste. Cell mass from many industrial fermentations today is often sold into animal feed markets. For example, the cell mass from a corn dry mill ends-up in the DDGS product used primarily for ruminant feeds, while the cell mass from citric acid production can sometimes be sold as a poultry feed ingredient. On the other hand, if the cell mass cannot be sold then it has to be treated as a negative value waste. Digestion, compositing, landfill, and incineration 12

16 are some possible options for treatment. Assigning a zero value to the cell mass is a reasonable assumption for a preliminary analysis since its value is unknowable at this time. 5) Nutrient Costs: I assumed zero costs for nutrients. It is difficult to estimate costs since nutrient requirements of the organism are unknown and the nutrient content of the feedstock is unknown. As a comparison, current bioethanol models project a nutrient cost of about $0.03 per gallon. 6) Plant Scope: The analysis assumed a battery limits plant that purchased utilities from a host facility. Capital costs for a stand-alone plant could easily be double the costs for a battery limits plant. This, of course, will vary quite a bit depending upon the details of the situation. Please let me know if there are any other issues that need to be addressed. Sincerely, Tim Eggeman 13

17 REPORT DOCUMENTATION PAGE Form Approved OMB No The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Executive Services and Communications Directorate ( ). Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION. 1. REPORT DATE (DD-MM-YYYY) May REPORT TYPE Subcontract Report 4. TITLE AND SUBTITLE Boundary Analysis for H 2 Production by Fermentation 3. DATES COVERED (From - To) July 2001 September a. CONTRACT NUMBER DE-AC36-99-GO b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) T. Eggeman 5d. PROJECT NUMBER NREL/SR e. TASK NUMBER HY f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Neoterics International 2319 S. Ellis Ct. Lakewood, CO PERFORMING ORGANIZATION REPORT NUMBER LCO SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) National Renewable Energy Laboratory 1617 Cole Blvd. Golden, CO DISTRIBUTION AVAILABILITY STATEMENT National Technical Information Service U.S. Department of Commerce 5285 Port Royal Road Springfield, VA SUPPLEMENTARY NOTES NREL Technical Monitor: M.K. Mann 10. SPONSOR/MONITOR'S ACRONYM(S) NREL 11. SPONSORING/MONITORING AGENCY REPORT NUMBER NREL/SR ABSTRACT (Maximum 200 Words) This report, prepared for DOE s Hydrogen, Fuel Cells & Infrastructure Technologies Program, presents a boundary analysis for the production of hydrogen via fermentation of glucose or other carbohydrates. The Program s hydrogen production cost target goals cannot be met due to the high feedstock cost. The potential for lower-cost sugars to meet cost targets should be investigated. 15. SUBJECT TERMS Hydrogen Production; Fermentation; Economic Analysis 16. SECURITY CLASSIFICATION OF: 17. LIMITATION 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON OF ABSTRACT OF PAGES a. REPORT b. ABSTRACT c. THIS PAGE Unclassified Unclassified Unclassified UL 19b. TELEPONE NUMBER (Include area code) Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18